Gooch and McClenahan — Typical Hydrous Chlorides. 367 



eter, so that the temperature of the material in the boat might 

 be indicated by the thermometer as nearly as possible. Through 

 one tube was drawn slowly a current of air purified by caustic 

 potash and sulphuric acid, and through the other was sent a 

 slow current of hydrogen chloride, generated in a Kipp gen- 

 erator by the action of sulphuric acid upon sublimed ammonium 

 chloride in lumps. At the expiration of a definite period, the 

 boat was withdrawn, placed in a desiccator and weighed after 

 a suitable interval for cooling. The residue in the boat was 

 dissolved in water, acidulated with nitric acid and the chlorine 

 in it was precipitated by silver nitrate, the silver chloride being 

 weighed on asbestos. Thus it was possible to determine directly 

 the loss of water and chlorine from individual portions of the 

 salt under experimentation during definite intervals and at 

 fixed temperatures, both in an atmosphere of hydrogen chloride 

 and in air, and to find for each individual portion under experi- 

 ment what proportion of the total loss was hydrogen chloride 

 and what was water. The tabular statements and the diagrams 

 show the course of decomposition of the various salts for the 

 temperatures indicated. 



Hydrous JBarium Chloride. 



For the experiments with barium chloride a well-crystallized 

 specimen showing by analysis a normal content of chlorine was 

 taken. During the process of dehydration at temperatures 

 ranging as high as 100°, at which point all water was expelled, 

 there is no evidence of loss of chlorine, and the course of 

 dehydration, as would be anticipated, appears to be wholly 

 uninfluenced by the presence of hydrogen chloride. 



The slight iucrease in the chlorine generally found in the 

 salt after exposure to the atmosphere of hydrogen chloride may 

 be properly attributed to occlusion or adsorption of hydrogen 

 chloride. The data of individual experiments are gathered in 

 Table I, p. 368, and the general course of action is followed 

 in the diagram. 



Hydrous Magnesium Chloride. 



Similar experiments, the data of which are given in Table 

 II, were made with hydrous magnesium chloride dried in vacuo 

 over sulphuric acid and of nearly ideal constitution. 



So far as these results go, it appears that the loss of chlorine 

 during the process of dehydration of the hydrous magnesium 

 chloride, MgC] 2 '6II 2 0, is generally small until a temperature 

 approximating 200° is reached; that at temperatures between 

 100° and 130° hydrogen chloride generally restrains dehydra- 

 tion, while above that temperature dehydration progresses more 



